Heretofore, many kinds of sensors have been developed. Typical are sensors which can detect such variables as light, pressure, stress, position, distance, acceleration, temperature, humidity, hardness, shape, vibration (frequency), weight, rate of flow, quantity of gas, type of gas, quantity of electromagnetic energy, odor, or changes in such variables. Generally, these physical variable sensors consist of a sensor component to detect the physical variable and an electrical processor circuit component to electrically transform the output of the sensor component. The structural components of a physical variable sensor are enclosed in a case, and connections within the case are made with electrical wiring such as vinyl insulated cable. With this type of existing sensor, it is difficult to downsize the individual components and interconnect components with the existing wiring process, and the sensor component itself must be kept relatively large.
Furthermore, existing sensors require a different type of sensor component for each variable to be detected. Different types of outputs are produced by the sensor component including voltage, current, power, charge, resistance, or degree of change in these variables. Such sensors process each type of output with a dedicated circuit to measure each different variable.
As examples of existing physical variable sensors, consider a temperature sensor using a thermocouple and a light sensor using a photodiode. In the temperature sensor, the electromotive force generated in the thermocouple by temperature variation is processed by an electrical circuit so that it can be outputted as temperature. In the light sensor, light striking the photodiode generates a photocurrent, which is processed by an electrical circuit to detect the intensity of light, or the presence, position, or shape of an object. As can be understood from these examples, different types of sensors require different dedicated processor circuits. To design and build a dedicated processor circuit for each type of sensor, increases the production cost. Furthermore, the requirement for dedicated processor circuits prevents producing a multi-function sensor which can detect data relating to a number of different variables.